Commit fb7589a1 authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by David S. Miller
Browse files

tun: Add ability to create tun device with given index 



Tun devices cannot be created with ifidex user wants, but it's
required by checkpoint-restore project.

Long time ago such ability was implemented for rtnl_ops-based
interface for creating links (9c7dafbf net: Allow to create links
with given ifindex), but the only API for creating and managing
tuntap devices is ioctl-based and is evolving with adding new ones
(cde8b15f tuntap: add ioctl to attach or detach a file form tuntap
device).

Following that trend, here's how a new ioctl that sets the ifindex
for device, that _will_ be created by TUNSETIFF ioctl looks like.
So those who want a tuntap device with the ifindex N, should open
the tun device, call ioctl(fd, TUNSETIFINDEX, &N), then call TUNSETIFF.
If the index N is busy, then the register_netdev will find this out
and the ioctl would be failed with -EBUSY.

If setifindex is not called, then it will be generated as before.

Signed-off-by: default avatarPavel Emelyanov <xemul@parallels.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5f1cd200

drivers/net/tun.c

+20 −1
Original line number Diff line number Diff line
@@ -138,7 +138,10 @@ struct tun_file { 
	struct fasync_struct *fasync;

	/* only used for fasnyc */

	unsigned int flags;

	union {

		u16 queue_index;

		unsigned int ifindex;

	};

	struct list_head next;

	struct tun_struct *detached;

};
@@ -1601,6 +1604,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) 


		dev_net_set(dev, net);

		dev->rtnl_link_ops = &tun_link_ops;

		dev->ifindex = tfile->ifindex;



		tun = netdev_priv(dev);

		tun->dev = dev;
@@ -1817,6 +1821,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd, 
	kgid_t group;

	int sndbuf;

	int vnet_hdr_sz;

	unsigned int ifindex;

	int ret;



	if (cmd == TUNSETIFF || cmd == TUNSETQUEUE || _IOC_TYPE(cmd) == 0x89) {
@@ -1851,6 +1856,19 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd, 
			ret = -EFAULT;

		goto unlock;

	}

	if (cmd == TUNSETIFINDEX) {

		ret = -EPERM;

		if (tun)

			goto unlock;



		ret = -EFAULT;

		if (copy_from_user(&ifindex, argp, sizeof(ifindex)))

			goto unlock;



		ret = 0;

		tfile->ifindex = ifindex;

		goto unlock;

	}



	ret = -EBADFD;

	if (!tun)
@@ -2099,6 +2117,7 @@ static int tun_chr_open(struct inode *inode, struct file * file) 
	rcu_assign_pointer(tfile->tun, NULL);

	tfile->net = get_net(current->nsproxy->net_ns);

	tfile->flags = 0;

	tfile->ifindex = 0;



	rcu_assign_pointer(tfile->socket.wq, &tfile->wq);

	init_waitqueue_head(&tfile->wq.wait);

include/uapi/linux/if_tun.h

+1 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ 
#define TUNGETVNETHDRSZ _IOR('T', 215, int)

#define TUNSETVNETHDRSZ _IOW('T', 216, int)

#define TUNSETQUEUE  _IOW('T', 217, int)

#define TUNSETIFINDEX	_IOW('T', 218, unsigned int)



/* TUNSETIFF ifr flags */

#define IFF_TUN		0x0001

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